Snap action vane



June 28, 1955 J. w. WELSH 2,712,045

SNAP ACTION VANE.

Filed Aug. 18, 1953 2 Sheets-Sheet l V INVENTOR 8 A AORNEY United rates Patent 0*" SNAP ACTION VANE James W. Welsh, Summit, N. L, assignor to Signal-Stat Corporation, Brooklyn, N. Y., a corporation of New York Application August 18, 1953, Serial No. 374,975

12 Claims. (Cl. 290-122) This invention relates to flashers for electric lamp circuits and, more particularly, to an improved and simplified alternating flasher effective to make and break relatively heavy loads without time delay between breaking the circuit for one load and closing the circuit for the alternate load.

Generally speaking, two types of flashers are utilized in lamp flashing circuits, such as the signalling circuits for automotive vehicles. One type of flasher merely periodically opens and closes a single lamp circuit. The other type of flasher is arranged to alternately connect two different lamp circuits to a source of power so that the two circuits are flashed alternately and their lamps thus flashed in alternation with each other. This latter type is known as an alternate flasher or alternating flasher.

As hitherto constructed, such alternate flashers have had limitations inherent therein which have considerably reduced the number of potential applications. For example, the make and break action of the contacts of such flashers has not been sufliciently rapid to prevent substantial arc formation with consequent accelerated contact deterioration. Additionally, the duty cycle required of such flasher has dictated the use of relatively light current carrying members which has, correspondingly, limited the loads which could be handled by the flasher.

The present invention is directed to a novel and improved alternating flasher in which the foregoing limitations have been obviated. The movable elements switching the connections alternately between two lamp circuits are designed to maintain full contact pressure right up to the time the circuit connections are switched from one lamp or load circuit to the other. At the instant of switching, the circuit changing elements have a snap action resulting in substantially simultaneous switching of the contacts from one circuit to the other.

In my co-pending application, Serial No. 374,976, filed August 18, 1953, for Snap Action Device, I have shown and described a novel snap action vane of a relatively thin spring metal which may be incorporated in a snap action switch. This vane is provided with an initial deformation about a right line extending across the vane by thinning or deforming the vane along this line in two or more spaced sections of the line, these sections being spaced at their inner ends from the center of the vane and also preferably spaced from the outer ends of the line. When such a vane is to be utilized in a snap action switch, such as a flasher, the vane is forcibly bent about another line, at an angle to the line of initial deformation by applying force to the ends of such lines of initial deformation. When such force is released, the vane snaps back to its initial position, the action closely resembling that of a toggle.

With a vane initially deformed in such a manner, the locked up stresses or forces have loci on elliptical lines or Zones having radii centered on the center or mid point of the vane located on the line of initial deformation midway between the inner ends of the spaced ice or discontinuous deformation. If the vane is held or fixed at a point on one of these loci, the remainder of the vane, during snapping thereof, pivots about such mounting point. The greatest effective force is exerted at the center of the loci, but very substantial force is also exerted by portions of the vane located on the loci at the opposite side or" the deformation line from the fixed mot ting point.

Such a vane may be effectively used in a thermostatic snap action switch by restraining the vane in the stressderormed position by attaching a high resistance wire or strip at each of its ends to the vane at the ends of the line of initial bending. This high resistance wire or strip thus forcibly holds the vane in a distorted position bent about line angularly reiated to the line of initial bending. When the high resistance wire has electric current passing therethrough, it beats and expands. During the expansion of the wire, a point is reached at which the tension exerted by the wire is over-balanced by the kinetic energy of the vane stored therein by bending the latter from its initial bent condition. At this point, the vane snaps back to its initially bent condition.

When the wi e is holding the vane in the stressde'r'ormed position with the vane bent on a line at an angle to the line of initial deformation, the wire is spaced from the vane except at its attachment points thereto. As the wire expands to the point where the vane snaps back to its original pro-set or restored position, the wire snaps into linear contact with the vane. The wire, intermediate its end or vane attachment points, thus has movement inward and outward relative to the vane during the snappin action of the latter, and particularly relative to the mounting or pivoting point of the vane. Thereby, a make and break switch action can be provided by mounting one contact of the switch on the wire intermediate its ends, and mounting the cooperative contact in fixed relation to the vane mounting or pivot point, as by mounting the vane contact on a relatively rigid bracket or mounting member secured to the vane at a point laterally of the deformation line or on one of the stress contraction loci.

An on-off type thermostatic switch controlling a single load circuit is illustrated in said co-pending application. My co-pending application Serial No. 374,918, filed August 18, 1953, illustrates such a snap action switch or flasher having parameters such that the two contacts are held in full pressure engagement, or even under increasing pressure, during the time the resistance wire is heating and expanding and right up to the instant that the vane shapes back to its preset condition. Thus, there is no diminution or reduction of contact pressure during the initial part of the switch opening movement or cycle, and full pressure is maintained between the contacts until they are snapped apart by the snap action of the vane in restoring itself to its present deformation.

More specifically, the switch parameters are so selected that, when the contacts are engaged, and up to the time that the snap action takes place, the resistance wire is depressed at its center toward the vane, so that the center of the wire exerts a force component in the direction of the contact carried by the vane mounting means. By proper selection of the switch parameters, this contact pressure effecting force may be made to increase during the expansion of the resistance wire so that at least full contact pressure is maintained up to the instant the snap action of the vane occurs.

At such instant, the contacts are snapped apart, thus instantaneously moving the contacts from the full pressure engaged position to a widely separated circuit breaking position. Thereby, with such arrangement, a plot of the current flowing across the contacts versus time will essentially resemble a square wave portion of the curve to the current portion of the curve.

In accordance with the present invention, advantage is taken of the movement of the free portion of the vane relative to the vane pivot point to provide an alternating flasher for making and breaking a pair of heavy current drawing circuits alternately with a snap action switching between the two circuits. This arrangement may be incorporated in the switch shown in either of my said two co-pending applications, and preferably is incorporated in the contact pressure maintaining arrangement of my application Serial No. 374,918.

To provide the alternating switch action, an additional or third contact is mounted on the free portion of the vane moved relative to the vane pivot during snapping of the vane. This contact is disposed for cooperation with a further, or fourth, contact fixed relative to the vane pivot.

For best results, the third contact should be mounted at the point of the free portion of the vane where the maximum pressure is available. However, this point is at the center of the vane and, if the third contact were located at the center, there would be interference with the vane action. It has been found that adequate contact pressure conditions with the necessary spring action can be obtained by mounting the third contact at a point on the vane on the opposite side of the deformation line from the vane pivot point, and preferably on one of the elliptical stress loci. By mounting this third contact on the surface of the vane opposite the surface secured to the vane mounting bracket, the third and fourth contacts will be snapped into engagement as the resistance wire mounted contact is snapped out of engagement with the bracket mounted contact. Thus, one load circuit is snapped closed simultaneously with the snapping open of the other load circuit.

Due to the snap action of the vane, and also to the relatively large cross sectional area of the current carrying parts of the switch structure, such as the vane and its mounting bracket, substantially heavier loads can be handled than is possible with present alternating flashers. By eliminating the wire carried and bracket mounting contacts, and mounting the vane carried contact on the same surface of the vane as the mounting bracket, a single action or on-off flasher can be provided.

For an understanding of the invention principles, reference is made to the following description of a typical embodiment thereof as illustrated in the accompanying drawings.

In the drawings:

Fig. l is a perspective view of a snap action vane used in the invention flasher;

Fig. 2 is a drawing reproduced from a photograph made, with polarized light, of the vane of Fig. 1 formed of transparent material, showing the elliptical stress concentration loci adjacent the vane center;

Fig. 3 is a perspective view of a snap action vane and attached mounting member used in the invention flasher;

Fig. 4 is a plan view of the invention flasher with the resistance wire contracted;

Fig. 5 is an elevation view of the invention flasher;

Fig. 6 is a sectional view on the line 6-6 of Fig. 5; and

Figs. 7a through 7h are graphical illustrations of the snap action of the vane.

Referring to Fig. l which is substantially identical with Fig. 4 of my said co-pending application Serial No. 374,976, a snap action vane it is illustrated which is identical with that shown and described therein. Vane 16 is preferably made of relatively thin spring metal, with consideration given to its spring factor, stiffness, temperature coefficient, and the like, in accordance with the desired rate of operation of the snap action.

To provide an initial set to vane 19 and to give the same some depth so that it will resemble a beam in its action,

the vane 16, which is shown as a substantially rectangular vane, is deformed or thinned along diagonal interconnecting corners 11 and 12. This vane or deformation is preferably effected by linearly embossing the vane along the line 11-12 in two elongated spaced portions or bosses 15. It will be noted that the bosses have their inner ends disposed substantially equal distances from the center of vane 10 so that the center area of the vane is left unrnarred. This greatly prolongs the life of vane 10 by removing the stress concentration from the center to a pair of points on bosses 15. If the deformation line 11-12 were continuous through the vane center area, the fiattening of the vane at the center during repeated cycles would eventually cause fatigue of the vane at the center and reduce the amount of force required to snap the vane between the illustrated position and another deformed position.

Due to the bosses 15, 15, the sections 13 and 1d of the vane on either side of line 11-12 bend upwardly so that the vane assumes the form of a shallow V having its apex on line 11-12. When vane bending forces are applied to the end of line 11-12, and the value of these forces equals or overbalances the inherent tendency of the vane to stay in its preset condition, the vane snaps into a new bent, or deformed position, forming another shallow V along the other diagonal 16-17. When the forces at points 11 and 12 are decreased to a point where they are overbalanced by the kinetic energy stored in vane 16 due to such distorting force, the vane snaps back to a position bent along the line 11-12.

Photographs, taken with polarized light, of a transparent vane formed in this manner show lines of force in the unmarred center area of the vane which comprise elliptical bands 13 having radii centered on the vane centcr, as shown in Fig. 2. if the vane is secured or sup ported at a point on one of these elliptical stress loci, the stress points on the vane during application of bending force at corners 11 and i2 occur within the length of bosses 15. Thus, the stresses are removed from the center area and distributed between two points spaced from the center. This greatly prolongs the period before fatigue takes place in the stressed section of the vane.

Advantage is taken of this fact by supporting the vane by electrically and mechanically securing the latter, at a point on one of such elliptical lines of force, to a relatively rigid electrically conductive mounting member or bracket 2%, as shown in Fig. 3. The point of attachment of the mounting member to the vane acts as a pivot point for the vane during its snap action, and is preferably spaced laterally of the initial bend line 11-12.

When the vane is used to form a snap action switch, the bending stresses may be conveniently applied to points Ill and 12 by means of a high resistance wire or strip 30 electrically and mechanically secured to these corners of the vane (Fig. 3). For this purpose, the points 11 and 12 are bent downwardly as illustrated in Fig. 3 and the ends of wire or strip 36 are secured thereto at 31 and 32, while the vane is bent along the line 16-17, so that the wire in its cold or contracted position holds the vane deformed into a V having its apex along diagonal 16-17. If w'ue 38 has electric current passed therethrough, it expands and, as the wire force is overbalanced by the restoring kinetic energy built up in vane 10, the vane snaps back to its initially bent condition along the line 11-12.

An arrangement for utilizing this action is illustrated in Figs. 4, 5 and 6, which show the invention alternating flasher. The center section 21 of mounting member of 29 has a band 23 of insulation Wrapped thereon and a band 24 of conductive metal is wrapped around band 23. Band 24 carries a contact point 25 at the intersection of mounting member 29 and wire 30. The wire 30 has a contact point secured to its mid-section for cooperation with contact 25'.

The free end of mounting member 29 is secured to a dielectric base 4% as by a rivet connecting the outer end 26 of member 20 to a prong or terminal 42 on base 40. Another prong or terminal 393 is connected by rivet 34 to a conductive strip id connected to band 2 In accordance with the invention, a third contact 55 is mounted on vane ill on the surface of the vane opposite to the surface secured to bracket 21 and on the opposite side of diagonal llll2 from the point of attachment of bracket 2%. Qontact 55 is preferably located on one of the stress loci 18. Due to its mounting on the free portion of the vane, contact moves relatively to bracket 2%, and thus relatively to base 41' during snapping of vane it). The contact is cooperative with a fourth contact 6t) mounted on the free or spring end 61 of a bracket 65 which is generally U shape and has a short leg 62 secured by a rivet 37 to a third terminal or prong 35 on base 4%. Bracket 65 has an. upright, intermediate bight 63 in continuation of leg as, and l tiger leg 61 extends from bight 63 over vane 30 to the mounting position of contact 55. Leg 431 may he stepped toward vane it) the proper amount to provide clearance for movement of the vane corners while positioning con tact 60 for engagement by contact 55. In the illustrated position, Wire 3% is contracted so that vane 163 is stressdeformed with its free portion pulled toward base 40. Contact 69 is thus separated from contact $5.

Referring to Fig. 6, a grounded battery 47 is connected, through a lamp control switch 45, to terminal 32 and thus to bracket 2% and vane it A conductor -ti connects terminal 33, and thus bracket mounted contact 25, to a grounded signal lamp SL-l representing a heavy current load. A conductor 46 connects terminal or prong 36, and thus contact 6%, to a second grounded signal lamp SL2 representing another relatively heavy current load.

Referring more particularly to Figs. and 6, the switch parameters are so selected that, in the contracted or cooled condition of wire 39, contacts 25 and 35 are en gaged and the relations of parts is such that the center part of wire 3%, carrying contact 35, is forced inwardly toward vane it). The wire thus assumes a shallow J as is shown in Fig. 2, and the tension of wire 3% thus in creases the force with which contacts 25 and 35 are held engaged.

When switch 45 is closed, current from battery t? flows through switch 45, terminal 5-2 and bracket 2 into vane at the mounting point or" the vane. The current flows from vane 1i) into both ends of wire 38 at points El and 32, and thus in parallel paths from the ends of wire 3% to contact 35. The current then flows through contact 25, band 24, conductor 44, rivet 34, terminal 33, conductor 46 and lamp SL-It, to ground. The current flowing through Wire 30 causes the latter to rapidly heat and expand, this wire preferably being Nichrome wire. As wire 30 expands and thus leng hens, the force exerted by the wire is finally overbalanced by the kinetic energy stored in vane 10, and the latter snaps to its initial or restored position bent along line ll12. This pulls wire 3 d outwardly relatively to bracket 2i) and into engagement with vane it to snap contacts 25 and 35 apart to break energizing circuit for lamp SL4 circuit. The wire 30 then cools and contracts. As the force exerted by the contracting wire overbalances the force tending to maintain vane It in its restored position, the vane again snaps to a position bent along line -437 wherein wire 30 snaps toward bracket 26 to reengage contacts and 35. The cycle then repeats.

As vane 10 snaps to the restored position to disengage contacts 25 and 35, the snap movement of its free portion simultaneously snaps contact into engagement with contact 6%. This completes an energizing circuit for lamp SL-2 from vane it) through contacts 55 and 6S, bracket 65, rivet 37, terminal 36, conductor 46', and lamp SL2 to ground. Contacts 5'5, as remain engaged while wire 3t) is cooled and reheated to the point where F3 it. snaps vane it) to the illustrated position to snap con tacts 55, 6t apart and snap contact 35 into engagement with contact 25. As the wire alternately expands and contracts, lamps SL1 and SL2 are thus flashed in alternation.

Referring now to Figs. 7a through 711, the action of the invention switch maintaining full contact pressure until the circuit break point is reached will be described as graphically illustrated. Before proceeding to this description, it should be mentioned that the mounting of contact 33 the mid-point of wire 30 has several important advantages. in the first place, the resistance is decreased due to the parallel circuits through wire 30. This enables the use of a wire rather than a ribbon for the high resistance element which facilitates the proper ext c second place, this contact position is LS6 the pressure in wire 30, thus assuring er snap action at the end of a cycle. A third advanis that this mounting of contact in effect provides lever between the center of the vane and the vane mounting point which comprise springs storing kinetic energy.

The relatively fixed mounting point of member 2t) is illustrated by the line F carrying the contact point 25. The lines a through 8 are reference lines graphically illustrating the lengthening and contracting of wire 3%). The lines 0-7 are scale lines indicating relative vertical movement of the ends of wire 3i relative to the fixed refcrence line F. The angle B is proportional to the vane diva deflection. This angle is also indicative of the contact pressure.

As shown, in the contracted position of wire 30 illustrated in 7a, the wire is bent into a shallow inverted V so that the force of the wire tends to increase the pressure between contacts 25 and 35, the wire 39 acting as a pressure increasing spring. In Fig. 70, wire 30 is cool is iust about to be heated. The vane apex is in an elevated condition illustrated by point M due to the mechanical advantage provided when vane 1b is secured at a stress loci point to bracket 29. The vane center is also raised due to the stress imparted thereto by the upward bending of wire 3% to increase the contact pressure. Wire 30 is contracted to its smallest length as indicated by its ends lying on lines aa. As the center of vane 10 is high, a small force in the wire will hold the vane due to the relatively large angle B of the toggle joint arrangement.

As the wire starts to heat, the parts assume the position of Fig. 7!). Wire 30 has increased in length to lines bb, and the center section of vane 10 is lowered to the line N due to flattening of the vane adjacent to its center sections. Wire 39 upon elongating tends to raise its ends but its center, being higher than its ends, as previously explained, is lower in Fig. 7b than in Fig. 7a, thus giving an over-all lowering of the vane ends from line 4 to a position between lines 4 and The lowering of the vane ends increases angle 2, thus increasing the contact pressure.

In Fig. 7c, wire St? has lengthened so that its ends are on the lies cc. The center section of vane 10 has moved down to line 0 and is approaching a flat condition so that its downward movement diminishes. However, the stored energy in the vane decreases, thus providing a new angular relationship. The pressure on contacts 25 and 35 remains substantially the same as in Fig. 7b. The wire relationship also remains about the same as in Fig. 7b. Angle 3 becomes smaller so that the tension in Wire 33 increases.

in 7c], th wire has lengthened so that its ends are at the lines nr/T, vane it} is approaching a flat condition, and wire 39 is under great stress. The vane center has lowered slightly. The contact pressure has increased due to the decrease in angle B and the vane is about to snap to its restored condition.

Fig. 7e shows the relation to parts immediately after such snapping or" the vane to change the apex of the V from line i617 to line 11-42. The relationship of Wire 30 to the mounting has changed, due to the snapping of vane 19, thus snapping open contacts and to break the circuit. The wire is essentially the same length as in Fig. 7d and angle B is quite small.

In Fig. 7f, wire 30 is contracting to build up pressure in the vane and increase the angle B. The vane angle is decreasing and the resultant is a build-up in pressure in wire 30, which has moved slightly in an upward direction. However, as the vane center is moving more than the wire, the resultant movement of wire St? is toward line F representing bracket 20.

In Fig. 7g, wire 30 is still contracting but is moving toward bracket 20 due to the diminishing of the upward movement of the vane center as it approaches the fiat condition. The stress in wire 30 has increased and the movement of the parts begins to accelerate. Angle B is increasing and thus building up kinetic energy in vane its.

Fig. 711 illustrates a position where wire 3:"; has contracted even further than the position shown in Fig. 7g

and vane 10 is about to snap to a bend along lines :i17 111i rectly on the free portion of the vane and the other cons..-

tact fixed relative to the vane pivot. Due to the relatively large masses of vane 10, bracket 20, and bracket 65, relatively heavy current drawing circuits can be effectively handled. The snap action of making and breaking the circuit greatly reduces contact deterioration.

While a specific embodiment of the invention has been shown and described in detail to illustrate the application of the invention principles, it will be understood that the invention may be embodied otherwise without departing from such principles.

What is claimed is:

1. An alternating snap action electric switch comprising, in combination, a substantially flat vane of relatively thin, electrically conductive spring metal having a substantially linear preset deformation extending thereacross, said deformation being interrupted intermediate its ends at points substantially equidistant from the vane center to leave the central area of the vane free of preset deformation; means mounting said vane at a point spaced laterally from said deformation whereby, under opposed bending stresses periodically applied to and released from points adjacent the outer ends of said deformation, in directions parallel to said deformation, to effect snapping of the vane between a stress-deformed position, in which the vane is bent about a line therein bisecting the line of deformation at an angle of substantially 90, and a restored initial preset position, the free portion of said vane will pivot about said mounting point; a pair of first contacts electrically and mechanically connected to the free portion of said vane and on opposite surfaces of the latter; a pair of second contacts each fixed relative to the mounting point of said vane and each arranged to be engaged by a different one of said first contacts, said second contacts being insulated from each other; one of said second contacts being engaged by its associated first contact in the stress-deformed position of the vane and the other of said second contacts being engaged by its associated first contact in the restored position of the vane; and means operable to alternately apply and release vane bending stresses at points adjacent the outer ends of said deformation.

2. An alternating snap action electric switch comprising, in combination, a substantially flat vane of relatively thin, electrically conductive spring metal having a substantially linear preset deformation extending thereacross, said deformation being interrupted intermediate its ends at points substantially equidistant from the vane center to leave the central area of the vane free of preset deformation; means mounting said vane at a point spaced laterally from said deformation whereby, under opposed bending stresses periodically applied to and released from points adjacent the outer ends of said deformation, in directions parallel to said deformation, to effect snapping of the vane between a stress-deformed position, in which the vane is bent about a line therein bisecting the line of deformation at an angle of substantially 90, and a restored initial preset position, the free portion of said vane will pivot about said mounting point, a pair of first contacts electrically and mechanically connected to the free portion of said vane and on opposite surfaces of the latter; a pair of second contacts each fixed relative to the mountingpoint of said vane and each arranged to be engaged by a different one of said first contacts, said second contacts being insulated from each other; one of said second contacts being engaged by its associated first contact in the stress-deformed position of the vane and the other of said second contacts being engaged by its associated first contact in the restored position of the vane; and electrically energized means operable to alternately apply and release vane bending stresses at points adjacent the outer ends of said deformation.

3. An alternating snap action electric switch comprising, in combination, a substantially flat vane of relatively thin, electrically conductive spring metal having a substantially linear preset deformation extending thereacross, said deformation being interrupted intermediate its ends at points substantially equidistant from the vane center to leave the central area of the vane free of preset deformation; means mounting said vane at a point spaced laterally from said deformation whereby, under opposed bending stresses periodicaly applied to and released from points adjacent the outer ends of said deformation, in directions parallel to said deformation, to effect snapping of the vane between a stress-deformed position, in which the vane is bent about a line therein bisecting the line of deformation at an angle of substantially 90, and a restored initial preset position, the free portion of said vane will pivot about said mounting point, a pair of first contacts electrically and mechanically connected to the free portion of said vane and on opposite surfaces of the latter; a pair of second contacts each fixed relative to the mounting point of said vane and each arranged to be engaged by a different one of said first contacts, said second contacts being insulated from each other; one of said second contacts being engaged by its associated first contact in the stress-deformed position of the vane and the other of said second contacts being engaged by its associated first contact in the restored position of the vane; and electrically energized thermostatic means operable to alternately apply and release vane bending stress at points adjacent the outer ends or" said deformation.

4. An alternating snap action electric switch comprising, in combination, a substantially flat vane of relatively thin, electrically conductive spring metal having a substantially linear preset deformation extending thereacross, said deformation being interrupted intermediate its ends at points substantially equidistant from the vane center to leave the central area of the vane free of preset deformation; means mounting said vane at a point spaced laterally from said deformation whereby, under opposed bending stresses periodically applied to and released from points adjacent the outer ends of said deformation, in directions parallel to said deformation, to effect snapping of the vane between a stress-deformed position,

in which the vane is bent about a line therein bisecting the line of deformation at an angle of substantially 90, and a restored initial preset position, the free portion of said vane will pivot about said mounting point; a pair of first contacts electrically and mechanically connected to the free portion of said vane and on opposite surfaces of the latter; a pair of second contacts each fixed relative to the mounting point of said vane and each arranged to be engaged by a different one of said first contacts, said second contacts being insulated from each other; one of said second contacts being engaged by its associated first contact in the stress-deformed position of the vane and the other of said second contacts being engaged by its associated first contact in the restored position of the vane; a heat expansible element secured at each end to said vane adjacent the outer ends of said deformation, in the contracted condition and bending said vane about a line bisecting said deformation at an angle of substantially 90 degrees, said element extending over the vane surface parallel to said deformation; and means for alternately heating and cooling said element to snap the vane between the stress-deformed and restored positions.

5. An alternating snap action electric switch comprising, in combination, a substantially flat vane of relatively thin, electrically conductive spring metal having a substantially linear preset deformation extending thereacross, said deformation being interrupted intermediate its ends at points substantially equidistant from the vane center to leave the central area of the vane free of preset deformation; means mounting said vane at a point spaced laterally from said deformation whereby, under opposed bending stresses periodically applied to and released from points adjacent the outer ends of said deformatiomun directions parallel to said deformation, to effect snapping of the vane between a stress-deformed position, in which the vane is bent about a line therein bis-ecting the line of deformation at an angle of substantially 99, and a restored initial preset position, the free portion of said vane will pivot about said mounting point; a pair of first contacts electrically and mechanically connected to the free portion of said vane and on opposite surfaces of the latter; a pair of second contacts each fixed relative to the mounting point of said vane and each arranged to be engaged by a different one of said first contacts, said second contacts being insulated from each other; one or said second contacts being engaged by its associated first contact in the stress-deformed position of the vane and the other of said second contacts being engaged by its associated first contact in the restored position of the vane; a heat expansihle electrically conductive element secured at each end to said vane adjacent the outer ends of said deformation, in the contracted condition and bending said vane about a line bisecting sa d deformation at an angle of substantially 90 degrees, said elementero tending over the vane surface parallel to said deiorniation; and means for alternately heating and cooling said element to snap the vane between the stress-deformed and restored positions; one of said first contacts being mounted on said element.

6. An alternating snap action electric switch comprising, in combination, a substantially flat vane of relativeiy thin, electrically conductive spring metal having a substantially linear preset deformation extending thereacross, said deformation being interrupted intermediate its ends at points substantially equidistant from the vane center to leave the center area of the vane free of preset deformation; a relatively rigid electrically conductive member mounting said vane at a point spaced laterally rrom said deformation whereby, under opposed bending stresses periodically applied to and released from po nts ad acent the outer ends of said deformation, in directions parallel to said deformation, to effect snapping of the vane between a stress-deformed position, in which the vane is bent about a line therein bisecting the line of deformation at an angle of substantially 90, and a restored initial preset position, the free portion of said vane will pivot about said mounting point; a pair of first contacts electrically and mechanically connected to the free portion of said vane and on opposite surfaces of the latter; a pair of second contacts each fixed relative to the mounting point of said vane and each arranged to be engaged by a different one of said first contacts; said second contacts being insulated from each other; one of said second contacts being engaged by its associated first contact in the stressdeformed position of the vane and the other of said second iii contacts being engaged by its associated first contact in the restored position of the vane; a heat expansible electrically conductive element secured at each end to said vane adjacent the outer ends of said deformation, in the contracted condition and bending said vane about a line bisecting said deformation at an angle of substantially degrees, said element extending along the vane surface having said mounting member secured thereto and parallel to said deformation; and means for alternately heating and cooling said element to snap the vane between the stress-deformed and restored positions; one of said first contacts being mounted on said element and the second contact cooperable therewith being mounted on said member.

7. An alternating snap action electric switch comprising, in combination, a substantially fiat vane of relatively thin, electrically conductive spring metal having a substantially linear preset deformation extending thereacross, said deformation being interrupted intermediate its ends at points substantially equidistant from the vane center to leave the central area of the vane free of preset deformation; an electrically conductive member electrically connected to and mounting said vane at a point spaced laterally from said deformation whereby, under opposed bending stresses periodically applied to and released from points adjacent the outer ends of said deformation, in directions parallel to said deformation, to effect snapping of the vane between a stress-deformed position, in which the vane is bent about a line therein bisecting the line of deformation at an angle of substantially 90, and a restored initial preset position, the free portion of said vane will pivot about said mounting point; a heat expansible high resistance electrically conductive element electrically and mechanically secured at each end to said vane adjacent the outer ends of said deformation, in the contracted condition and bending said vane about a line bisecting said deformation at an angle of substantially 90 degrees, said element extending along the vane surface having said mounting member secured thereto and parallel to said deformation; a pair of first contacts, one mounted on the outer side of and in circuit connection with said element and the other mounted on the free portion of said vane on the surface thereof opposite that having said mounting member secured thereto; a pair of second contacts, one mounted in insulated relation on said member and cooperable with the element-supported first contact and the other fixed relative to the mounting member and cooperable with the vane-mounted first contact; said element-and-member-supported contacts being engaged in the stress-deformed condition of said vane and the other set of contacts being engaged in the restored condition of the vane; and means operable to effect alternate heating and cooling of said element to snap said vane to alternately engage each first contact with its associated second contact.

8. An alternating snap action electric switch comprising, in combination, a substantailly flat vane of relatively thin, electrically conductive spring metal having a substantially linear preset deformation extending thereacross,

said deformation being interrupt-ed intermediate its ends at points substantially equidistant from the vane center to leave the central area of the vane free of preset deformation; an electrically conductive member electrically connected to and mounting said vane at a point spaced laterally from said deformation whereby, under opposed bending stresses periodically applied to and released from points adjacent the outer ends of said deformation, in directions parallel to said deformation, to effect snapping of the vane between a stress-deformed position, in which the vane is bent about a line therein bisccting the line of deformation at an angle of substantially 90, and a restored initial preset position, the free portion of said vane will pivot about said mounting point; a heat expansible high resistance electrically conductive element electrically and mechanically secured at each end to said vane adjacent the outer ends of said deformation, in the contracted condition and bending said vane about a line bisecting said deformation at an angle of substantially 90 degrees, said element extending along the vane surface having said mounting member secured thereto and parallel to said deformation; a pair of first contacts, one mounted on the outer side of and in circuit connection with said element and the other mounted on the free portion of said vane on the surface thereof opposite that having said mounting member secured thereto and on the opposite side of said deformation from the latter; a pair of second contacts, one mounted in insulated relation on said member and cooperable with the element-supported first contact and the other fixed relative to the mounting member and cooperable with the vane-mounted first contact; said element-and-member-supported contacts being engaged in the stress-deformed condition of said vane and the other set of contacts being engaged in the restored condition of the vane; and means operable to effect alternate heating and cooling of said element to snap said vane to alternately engage each first contact with its associated second contact.

9. An alternating snap action electric switch comprising, in combination, a substantially flat vane of relatively thin, electrically conductive spring metal having a substantially linear preset deformation extending thereacross, said deformation being interrupted intermediate its ends at points substantially equidistant from the vane center to leave the central area of the vane free of preset deformation and with elliptical stress concentration loci radiating from the vane center; an electrically conductive member electrically connected to and mounting said vane at a point on one of said loci spaced laterally from said deformation whereby, under opposed bending stresses periodically applied to and released from points adjacent the outer ends of said deformation, in directions parallel to said deformation, to effect snapping of the vane between a stress-deformed position, in which the vane is bent about a line therein bisecting the line of deformation at an angle of substantially 90, and a restored initial preset position, the free portion of said vane will pivot about said mounting point; a heat expansible high resistance electrically conductive element electrically and mechanically secured at each end to said vane adjacent the outer ends of said deformation, in the contracted condition and bending said vane about a line bisecting said deformation at an angle of substantially 90 degrees, said element extending along the vane surface having said mounting member secured thereto and parallel to said deformation; a pair of first contacts, one mounted on the outer side of and in circuit connection with said element and the other mounted on the free portion of said vane on the surface thereof opposite that having said mounting member secured thereto; a pair of second contacts, one mounted in insulated relation on said member and cooperable with the element-supported first contact and the other fixed relative to the mounting member and cooperable with the vane-mounted first contact; said element-and-member-supported contacts being engaged in the stress-deformed condition of said vane and the other set of contacts being engaged in the restored condition of the vane; and means operable to effect alternate heating and cooling of said element to snap said vane to alternately engage each first contact with its associated second contact.

10. An alternating snap action electric switch comprising, in combination, a substantially flat vane of relatively thin, electrically conductive spring metal having a substantially linear preset deformation extending thereacross, said deformation being interrupted intermediate its ends at points substantially equidistant from the vane center to leave the central area of the vane free of preset deformation and with elliptical stress concentration loci radiating from the vane center; an electrically conductive member electrically connected to and mounting said vane at a point on one of said loci spaced laterally from said deformation whereby, under opposed bending stresses periodically applied to and released from points adjacent the outer ends in said deformation, in directions parallel to said deformation, to effect snapping of the vane between a stress-deformed position, in which the vane is bent about a line therein bisecting the line of deformation at an angle of substantially 90, and a restored initial preset position, the free portion of said vane will pivot about said mounting point; a heat expansible high resistance electrically conductive element electrically and mechanically secured at each end to said vane adjacent the outer ends of said deformation, in the contracted condition and bending said vane about a line bisecting said deformation at an angle of substantially 90 degrees, said element extending along the vane surface having said mounting member secured thereto and parallel to said deformation; a pair of first contacts, one mounted on the outer side of and in circuit connection with said element and the other mounted on the free portion of said vane on the surface thereof opposite that having said mounting member secured thereto, and on the opposite side of said deformation from the latter; a pair of second contacts, one mounted in insulated relation on said member and cooperable with the element-supported first contact and. the other fixed relative to the mounting member and cooperable with the vane-mounted first contact; said element and member supported contacts being engaged in the stress-deformed condition of said vane and the other set of contacts being engaged in the restored condition of the vane; and means operable to effect alternate heating and cooling of said element to snap said vane to alternately engage each first contact with its associated second contact.

11. An alternating snap action electric switch comprising, in combination, a substantially fiat and rectangular vane of relatively thin, electrically conductive spring metal having a substantially linear preset deformation extending rhereacross along a diagonal, said deformation being interrupted intermediate its ends at points substantially equidistant from the vane center to leave the central area of the vane free of preset deformation and with elliptical stress concentration loci radiating from the vane center; an electrically conductive member electrically connected to and mounting said vane at a point on one of said loci spaced laterally from said deformation whereby, under opposed bending stresses periodically applied to and released from points adjacent the outer ends of said deformation, in directions parallel to said eformation, to effect snapping of the vane between a stress-deformed position, in which the vane is bent about a line therein bisecting the line of deformation at an angle of substantially 90, and a restored initial-preset position, the free portion of said vane Will pivot about said mounting point; a heat expansible high resistance electrically conductive element electrically and mechanically secured at each end to said vane adjacent the outer ends of said deformation, in the contracted condition and bending said vane about a line bisecting said deformation at an angle of substantially 90 degrees, said element extending along the vane surface having said mounting member secured thereto and parallel to said deformation; a pair of first contacts, one mounted on the outer side of and in circuit connection with said element and the other mounted on the free portion of said vane on the surface thereof opposite that having said mounting member secured thereto; a pair of second contacts, one mounted in insulated relation on said member and cooperable with the element-supported first contact and the other fixed relative to the mounting member and cooperable with the vane-mounted first contact; said elemcnt-and-member-supported contacts being engaged in the stress-deformed condition of said vane and the other set of contacts being engaged in the restored condition of the vane; and means operable to effect alternate heating and cooling of said element to snap said vane 13 to alternately engage each first contact with its associated second contact.

12. An alternating snap action electric switch comprising, in combination, a substantially fiat and rectangular vane of relatively thin, electrically conductive spring metal having a substantially linear preset deformation extending thereacross along a diagonal, said deformation being interrupted intermediate its ends at points substantially equidistant from the vane center to leave the central area of the vane free of preset deformation and with elliptical stress concentration loci radiating from the vane center; an electrically conductive member electrically connected to and mounting said vane at a point on one of said loci spaced laterally from said deformation whereby, under opposed bending stresses periodically applied to and released from points adjacent the outer ends of said deformation, in directions parallel to said deformation, to effect snapping of the vane between a stress-deformed position, in which the vane is bent about a line therein bisecting the line of deformation at an angle of susbtantially 90, and a restored initial preset position, the free portion of said vane will pivot about said mounting point; a heat expansible high resistance electrically conductive element electrically and mechanically secured at each end to said vane adjacent the outer ends of said deformation, in the contracted condition and bending said vane about a line bisecting said deformation at an angle of substantially 90 degrees, said element extending along the vane surface having said mounting member secured thereto and parallel to said deformation; a pair of first contacts, one mounted on the outer side of and in circuit connection with said element and the other mounted on the free portion of said vane on the surface thereof opposite that having said mounting member secured thereto, and on the opposite side of said deformation from the latter; a pair of second contacts, one mounted in insulated relation on said member and cooperable with the element-supported first contact and the other fixed relative to the mounting member and cooperable with the vane-mounted first contact; said elementand-member-supported contacts being engaged in the stress-deformed condition of said vane and the other set of contacts being engaged in the restored condition of the vane; and means operable to effect alternate heating and cooling of said element to snap said vane to al ternately engage each first contact with its associated second contact.

References Cited in the file of this patent UNITED STATES PATENTS 2,249,837 Lee July 22, 1941 2,338,515 Johns Ian. 4, 1944 2,616,996 Beeman Nov. 4, 1952 

